A communication network, known as an "intranet," typically provides high-speed information communications among a group of user terminals, e.g., those of a single entity, such as a corporation. Such an intranet is often provided with an access connection to the Internet, by which the various terminals attached to the intranet can obtain information from the Internet. Techniques have been developed to efficiently utilize the often high-speed bandwidth of such an access connection.
One such technique involves use of a proxy server in the intranet. In accordance with this technique, user terminals are connected via the intranet to a proxy server through which the Internet is accessed. Among other things, the proxy server includes a proxy cache which contains copies of objects, including web pages, recently accessed by the terminals. By employing a conventional web browser, a user at a terminal on the intranet may request an object available on the Internet.
In a well known manner, a local cache in the user terminal, which contains copies of objects recently accessed by that terminal only, is first searched for the requested object. If the object is not found there, the object request is then forwarded to the proxy server, where the proxy cache is searched for the object in question. Since the proxy cache (a) has a larger capacity than the local cache and (b) is shared by other terminals, the likelihood of locating the requested object, especially a popular object, in the proxy cache is higher. Only when it is determined that the requested object is not within the proxy cache, a condition known as a "cache miss," would the object request be transmitted to the Internet through the Internet access connection to obtain the object. Thus, by employing such a prior art technique, the volume of the access traffic to and from the Internet over the Internet access connection is reduced from what it would have been had each request had to be served from the Internet itself.
Efforts have been made to increase the proxy cache hit rate to more efficiently utilize the Internet access bandwidth. These efforts call for cooperation of proxy servers in different intranets. In one such effort, a requested object for which a cache miss has been determined is searched in one or more proxy caches of other cooperating servers. Such a search may be performed using a multicasting technique described in: Malpani et al., "Making World Wide Web Caching Servers Cooperate," World Wide Web Journal, vol. 1, Issue 1, Winter 1996, pp. 107-117. In another approach, a centralized database of the objects existing in the caches of cooperating servers is maintained to facilitate the object search. For details on this approach, one may refer to: S. Gadde et al., "Reduce, Reuse, Recycle: An approach to Building Large Internet Caches," Proceedings of the 1997 Conference on Hot Topics in Operating Systems, May 1997, pp. 93-98.